Comment 4 for bug 946663

I have the same problem. I did not install any additional drivers; Ubiquity and the release are the same version (12.04 beta 1) but I also have a non-formatted old filesystem as /home. I have / and /boot formatted as new btrfs partitions and /home as the old not-to-be-formatted reiserfs partition. /home is mounted and decrypted at /mnt/tmpmount at the time the installer hangs with the message 'Removing conflicting operating system files' and the button to skip this is greyed out.